Impact reducing safety systems are used in a plurality of applications where it is important to reduce impact energy, meaning absorbing at least part of the force released upon physical impact of an object, animals or humans, on the safety system. Impact reducing safety systems are for example vehicle bumpers and vehicle deformable zones, guardrails, reinforced security doors, concrete safety barriers, safety fences, etc.
It is known in the art that, in specific impact reducing safety systems, steel rope safety systems can be used. A specific example of a steel rope safety system used in an impact reducing safety system is a safety fence in for example loading dock areas, in factories, warehouses, and other industrial areas in which moving equipment such as lorries and forklifts are used. Safety fences are important to protect personnel, equipment, and goods, to prevent accidental collision, and to decrease the impact of a moving vehicle on the personnel, equipment, or goods if accidental collision still occurs. Such safety fence is also used for burglary protection where it reduces the impact of vehicles on store windows etc.
Another specific example of a steel rope safety system used in an impact reducing safety system are energy absorbing nets and steel ropes for attenuating impact energies from rock falls, as described in US-A1-2005205853.
Another specific example of a steel rope safety system used in an impact reducing safety system are guardrails which are installed along edges or medians of roadways and highways. According to U.S. Pat. No. 6,962,328 B2, guardrails including steel rope safety systems may reduce damage to an impacting vehicle and/or injury to occupants of the impacting vehicle as compared with other types of highway safety systems and highway barriers. Steel rope safety systems are often designed and installed with at least one steel rope mounted horizontally on a plurality of generally vertical support posts.
A recognized limitation of steel rope safety systems is the excessive deflection and elongation of the steel ropes upon impact. This is caused by closing of the outer wires of a strand around its rope and closing of the outer strands of the steel rope around its rope under tension. The closing action is the filling up of the spaces between the individual wires and the spaces between the strands. This phenomenon is called constructional stretch and has to be considered when installing the system. Nowadays, constructional stretch is decreased by pre-stretching the steel rope, usually from 30% up to 50%, before installing it in a steel rope safety system, thereby restricting further excessive deflection and elongation upon impact.
However, a disadvantage of pre-stretching the steel rope is that it may result in wire coating damage if done at relatively high temperatures and/or loads. Further, pre-stretching is an additional step in the steel rope manufacturing, which makes the manufacturing more expensive. Moreover, the constructional stretch removed during the pre-stretching operation may be re-induced as a result of final packaging and transportation effects. Another disadvantage is that pre-stretched steel rope safety systems still suffer from, although not excessive, but still severe elongation upon impact.
Given the above drawbacks of existing steel rope safety systems and methods, it is an object of the present invention to provide a steel rope safety system wherein steel rope pre-stretching can be avoided and still structural elongation upon impact can be diminished or even eliminated. In other words, a pre-stretched steel rope can be avoided; that is, a steel rope in a non-stretched condition can be provided, as will be readily appreciated by a person having ordinary skill in the art.
It is in particular an object of the present invention to provide a steel rope safety system wherein more tension is built up while keeping the same steel rope deflection upon impact compared to known steel rope safety systems.
It is further an object of the present invention to provide a steel rope safety system, wherein the same amount of tension is built up while decreasing steel rope deflection upon impact compared to known steel rope safety systems.
It is further an object of the present invention to provide a steel rope for use in impact reducing materials.
The present invention meets the above objects by using a compacted steel rope.